Transistors may be employed in a wide variety of electronic circuits including integrated circuits. Applications for transistors include amplifiers, digital processing circuits, RF circuits, DC circuits, and many other applications too numerous to mention.
A transistor may be vulnerable to breakdown caused by electrostatic discharge. For example, an electrostatic discharge may cause excessive current flow in the gate of a field-effect transistor (FET) and damage its gate structure. Breakdowns in an FET caused by electrostatic discharge may cause a failure of an entire integrated circuit as well as an entire electronic system or subsystem that employs a damaged FET.
One prior method for avoiding electrostatic discharge damage to an FET is to employ a relatively large resistor on the gate of the FET. A resistor at the gate of an FET may limit an amount of electrostatic discharge current into the FET and avoid damage to its gate structure. Unfortunately, a relatively large resistor on the gate of an FET may severely limit its performance in an amplifier application, e.g. by limiting gain and/or noise performance of an FET amplifier circuit.
Another prior method for avoiding electrostatic discharge damage to an FET is to employ diodes that limit an amount of reverse bias voltage on the gate of the FET. Unfortunately, diodes may hinder the performance of an FET amplifier and may not be practical in many other types of FET circuits.
Another prior method for avoiding electrostatic discharge damage to an FET is to employ capacitors that prevent electrostatic discharge current from reaching the gate of the FET. Unfortunately, the capacitors may not be practical in amplifier circuits and may increase the size and cost of integrated circuits.